5/6-7/12+9/20-11/30+13/42

来源：学生作业学帮网编辑：学帮网时间：2024/05/29 06:02:57

5/6-7/12+9/20-11/30+13/42
=(1/2+1/3)-(1/3+1/4)+(1/4+1/5)-(1/5+1/6)+(1/6+1/7)
=1/2+1/3-1/3-1/4+1/4+1/5-1/5-1/6+1/6+1/7
=1/2+1/7
=7/14+2/14
=9/14